Conservative Party leader Colin Craig has admitted that he smacks his daughter if she misbehaves, despite the law being clear there is no justification for the use of force as part of parental or caregiver discipline.

His party is a possible coalition partner for National after this year's general election and Mr Craig said - were he in the position to - he would want to negotiate repealing the so-called anti-smacking law that came into effect in 2007.

The legislation removed the defence of "reasonable force" for parents prosecuted for assault on their children.

During an interview on RadioLive today, Mr Craig was asked if he would start to smack his own children if the law was reversed.

"I occasionally do it now," he replied.

Mr Craig told APNZ he did not expect any backlash from the admission.

Polling by Curia Market Research of 1000 respondents last year covered the issue of whether the law banning smacking should be changed to smacking being a reasonable form of correction, with 77 per cent agreeing, he said.

Mr Craig conceded that did not necessarily mean the same numbers of parents were ignoring the law and smacking their children.

The law as it stood was too "ambiguous" because it said police would not prosecute a parent for a smack unless it was in the public interest, Mr Craig said.

He said the physical discipline of his child was technically against the law if police saw it in the public interest to prosecute.

"And how would I know what they think?"

He said mostly his discipline consisted of "a flick of a finger on the back of a knuckle".

"It hurts for a moment," he said.

The vast majority of discipline he used was not physical, he said.

A police spokesman said they were satisfied that Mr Craig's comments on radio this morning did not "amount to disclosure of an offence".

"Police do not intend being drawn into a political debate on this issue in an election year."

University of Auckland Associate Professor of Law Bill Hodge said even if police did not prosecute anyone could bring a private prosecution against Mr Craig if they believed he was breaking the law.

- Section 59 of the Crimes Act says: -

* Every parent of a child and every person in the place of a parent of the child is justified in using force if the force used is reasonable in the circumstances and is for the purpose of:

- preventing or minimising harm to the child or another person

- preventing the child from engaging or continuing to engage in conduct that amounts to a criminal offence

- preventing the child from engaging or continuing to engage in offensive or disruptive behaviour

- performing the normal daily tasks that are incidental to good care and parenting.

* Nothing in (the above section) or in any rule of common law justifies the use of force for the purpose of correction.

* To avoid doubt, it is affirmed that the police have the discretion not to prosecute complaints against a parent of a child or person in the place of a parent of a child in relation to an offence involving the use of force against a child, where the offence is considered to be so inconsequential that there is no public interest in proceeding with a prosecution.